Phosphate coating composition and method of coating metal therewith



PHOSPHATE COATING COMPOSITION AND METHOD OF COATING METAL THEREWITHRobert F. Ayres, Leonia, and Edward Heinzelman, .lr.,

Palisades Park, N. J., assignors to Oakite Products, Inc., New York, N.Y., a corporation of New York No Drawing. Application March 21, 1955,Serial No. 495,820

Claims. (Cl. 148-615) The invention relates to the production ofphosphate. coating on metals, and particularly to the production of suchcoatings containing phosphates of zinc or manganese. More especially, itrelates to compositions of matter adapted to be used in producing suchcoatings, and to the process of applying such compositions. It'contemplates in its more specific aspects the use of com- 2,790,740Patented Apr. 30, 1957 'ice 7 required to react with the zinc ormanganese, or in other words the ratio of free to total phosphoric acidshould be at least about 1 to 7, i3. ratio of 1 to 4.2 being preferablesThe minimum preferred amount of the oxidizing radical is at least 12% inthe case of the stronger oxidizing agents such as the chlorates, whilefor the positions containing, in addition to the phosphoric acid radicaland zinc or manganese, the nitric acid radical.

This application is a continuation-in-part of our application Serial No.289,002, filed May 20, 1952 now abandoned.

' We have found that improved phosphate coatings may be produced onferrous metals, aluminum, zinc and other metals by treating them with anaqueous solution of phosphating compositions containing substantialproportions of oxidizing agents as well as zinc or manganese to whichhave been added a small proportion of a cerium compound as anaccelerator for the deposition and conditioning of the coating.Phosphate coatings produced in the manner described herein will consistof fine, even, well integrated crystals in a thickness of as much as1000 mg. per square foot. The coatings impart corrosion'protection tothe base metal and also form a. surface with which paint will form astrong bond if the surface is to be painted. Such layers also act aslubricants or as aids in working metal coated therewith.

Cerium appears to be effective only when used in the presence ofsubstantial proportions of zinc or man ganese, and only when oxidizingagents, of a kind well known in the art, as shown, for example, in theThompson' Patent No. 2,312,855, are also present in substantial amounts.I v y Further objects and advantages of the invention will appear morefully from the following description. It has been found that excellentphosphate coatings can be produced by the addition of small amounts ofcerium compounds to phosphate coating compositions containingsubstantial amounts of zinc or manganese and of the nitric, chlon'c orother oxidizing radicals. The .ce rium may be present in various forms,but the preferred addition product is ceric sulfate, Ce(SO4)2 orHowever, other cerium compounds may also be used, including cerichydroxide, Ce(OH)4; ceric fluoride, CeF4.H2O; ceric hydrate, Ce(OH)3;ceric oxide, CeOz and the like.

In practicing the invention, as is usual in the art, the materialforshipment is made up in a concentrated aqueous solution, which maycontain from 15% up to about 60% of water. This concentrate is used byadding from 2 to 8' ounces per gallon of water for baths, while as lowas 1 ounce per gallon may be used for spray coating.

'The active coat-ingingredients should includei from about 10%toabout-40% of zinc or manganese, with phosphoric acid at least 15 inexcess of the amount i somewhat weaker nitrates a minimum of 15% is'desir-' able. Proportions of oxidizing radical as high as about 30% maybe used. The cerium should be within the range of 0.15% to 2%.

In the phosphate coating bath, the proportions may range, per gallon,from 0.06 to 2 ounces of zinc or manganese, from 0.07 to 1.4 ounces pergallon of the oxidizing radical, and from 0.009 to 0.10 ounce of cerium.

Of course, mixtures of zinc and manganese compounds, mixtures ofdifferent oxidizing agents and mixtures of different cerium compoundsmay be used.

The following compositions are examples of those which may be used inaccordance with the invention.

7 Composition A Material: Percent Zinc nitr 53 Phosphoric acid 38 Zincnxide 1 Ceric sul 2% Composition B Material: Percent Zinc nitrat 52Phosphoric acid 75% 40 Zinc oxide 7 Ceric hydr xi 1 Composition CMaterial: Percent Zinc oxide 23 Phosphoric acid 75 44 Sodium nitrate 32Ceric fluoride 1 Composition D Material: Percent Manganic hydroxide 23Phosphoric acid 75% 44 Sodium nitrat 32 Ceric oxide" 1 Composition EMaterial: Percent Manganous carbonate 35 Phosphoric acid 75 37 Sodium'nitrate 27 Ceric sulfate 1 Composition F Material: Percent Manganousnitrate 52 Phosphoric acid 75 37 Ceric oxide 1 Composition G Materials:Percent Zinc nitrate i V 43.6 Phosphoric acid 75% 30.9 Zinc oxide 4.7Ceric sulfate 1.3

Water 19.5

' Composition H Materials: Percent Zinc oxide 10.0

, Phosphoric acid 75% 39.0

Ceric sulfate 1.0

Sodium chlor 10.0

:Water 40.0

.3 Cemros q I Materials: Percent Zinc oxide 10.0 Phosphoric acid 75 Zincnitrate- Ceric oxide Sodium chlorate W --.--f"'t"r"r---rr-rr-frrrrComposition J Materials: Percent Zinc oxide 10.0 Phosphoric acid 75%39.0 Sodium perborate 3.0 Sodium pe'rsulf-ate 10.0 Ceric fluoride e u1.0 Water 37.0

Composition K Materials: Percent Zinc "-T.".'.--.'"!"?'.-.--- Phosphoricacid 75% 39.0 Sodium persulfate 10.0 Ceric sulfate a- 1.0 Water 40.0

It is possible to use other oxidizing agents along, in combinationwithchlorates or in combination with each other in the above examples.Examples of other oxidizing agents are: The oxy acids (nitric, nitrous,chromic, chloric and other halogen oxy-acids) and their salts; peroxidessuch as hydrogen peroxide, alkali and alkali earth metal peroxides,etc.; the higher valent acid oxides; the perborates; organic nitrates,nit-rose compounds; permanganic acid and its salts; per-sulfates andother per compounds.

The time required for coating is from 1 to 5 minutes.

In the use of these materials, if scale is present, pickling may berequired before coating. The metal surface should then be cleaned with asolvent-emulsion or alkali typo cleaner. The composition is then appliedfor the requisite time, the metal is rinsed with water and then with adilute phosphoric-chromic acid rinse.

The material is of general applicability, producing phosphate coatingson ferrous metals, aluminum, zinc and other metals as well as alloysthereof.

While we have described herein some embodiments of our invention, wewish it to-be understood that we do not intend to limit ourselvesthereby except within the 'scope of the claims hereto orhereinafterappended.

We claim:

1. A phosphate coating bath comprising an aqueous so t on n is n e sentally or ate and co ta ni P 15 1 Wat r t eas @btll t '0 ounce of a lea ometal s t d f m he ro p cons stin of Zi c and ng n e d me abeiusrrese... in the orm a compound, at least about 0.07 ounce of atleast one anion of an oxidizing compound, phosphoric acid in an amountat least 15% in excess of the amount necessary to react With such metal,and at least 0.0009ourice of cerium in the formof a compound. 1 v

2. A phosphate coating bath comprising an aqueous solution consistingessentially of water and containing, per gallon of water, about 0.06 toabout 2 ounces of at l a 9?? metal se ected from the group consisting ofz n nd manganese, aid metal e ng present in the form of a compound, atleast about 0.07. ounce to'about 1.4 ou o at eas one anion of an oxi iingo p 1 1 9 1 90 3914 ii! QB emountat least 15% in .excess 'of theamount necessary to react with such metal, and between about 0.0009ounce and 0.10 of cerium in the form of a compound.

3 A phosphate coating bath comprising an aqueous solution consistingessentially of water and containing, pergallon of Water, about 0.06 toabout 2 ounces of at lea t one metal c ed r m the .EIQPJ? emittin OfZing apd manganese, said metal being present in the form of a compound,about 0.09 to about 1.4 ounces of the nitrate ion, phosphoric acid in anamount at least 15% in excess of the amount necessary to react with suchmetal, and at least 0.0009 ounce of cerium in the form of a compound.

4. A phosphate coating bath comprising an aqueous solution consistingessentially of water and containing, per gallon of water, about 0.06 toabout 2 ounces of at least one metal selected from the group consistingof zinc and manganese, said metal being present in the form of acompound, at least about 0.07 ounce to about 1.4 ounces of at least oneanion of an oxidizing compound, phosphoric acid in such amount that theratio of free phosphoric acid to total phosphoric acid is at least 1 to7, and at least 0.0009 ounce of cerium in the form of a compound inwhich the cerium in the form of a compound is present in basic form.

5. A phosphate coating bath comprising an aqueous solution consistingessentially of water and containing, per gallon of water, about 0.06 toabout 2 ounces of at least one metal selected from the group consistingof zinc and manganese, said metal being present in the form of acompound, about 0.09 to about 1.4 ounces of the nit a e n, phosphor a inan mo a e s 1 in excess of the amount necessary to react with suchmetal, and between about 0.0009 ounce and 0.10 ounce of cerium in theform of a compound.

6. A phosphate coating composition essentially consisting of, as coatingingredients, at least 10% of at least one metal selected from the groupconsisting of zinc and manganese, said metal being present in the formof a compound, at least 1.2% of an anion of an oxidizing compound,phosphoric acid in such amount that the ratio of free phosphoric acid tototal phosphoric acid is at least 1 to 7, and at least 0.15% of ceriumin the form of a compound.

7. A phosphate coating composition essentially con sisting of, ascoating ingredients, at least 10% of at least one metal selected fromthe group consisting of zinc and manganese, said metal being present inthe form of a compound, at least 15% of'the nitrate ion, phosphoricacid'in such amount that the ratio of free phosphoric acid to totalphosphoric acid is at least 1 to 7, and at least 0.15% of cerium in theform of a compound.

\ 8. A phosphate coating composition essentially consisting of, ascoating ingredients, from 10% to 40% of at least one metal selected fromthe group consisting of zinc and manganese, said metal being present inthe form of a compound, from 12% to 30% of an anion of an oxid zin c mpop osph ric i i uch amount tha th at o 015 ree Phospho acid to total pphoric acid i tle st 1 to 7. and 0.15% o 2% of r m in the form eta compund A phospha e o ting ompos n n ial y ns s ng as coat ng in r i nts,from 10% to of at least one metal selected from the group consisting ofzinc and manganese, said metal being present in the form of a compound,from 15% to 30% of the nitrate ion, phosphoric acid in such amount thatthe ratio of free phosphoric acid to total phosphoric acid is at least 1to 7, and 0.15% to 2% of cerium in the form of a compound.

10. A method of coating metal which comprises bringing into contact withthe metal a material as claimed in claim 1 for a sufiicient length oftime to form a coating 9!! h m t l- References Cited in the file of thispatent UNITED STATES PATENTS 2,301,983 Tanner Nov. 17, 1942 2,314,565Thompson -Mar. 23, 1943 2 31 ,810 Rom g ----'-.--e Apr- 2 1 2,9 8, 266.Thirsk De 1954

1. A PHOSPHATE COATING BATH COMPRISING AN AQUEOUS SOLUTION CONSISTINGESSENTIALLY OF WATER AND CONTAINING, PER GALLON OF WATER, AT LEAST ABOUT0.06 OUNCE OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OFZINC AND MANGANESE, SAID METAL BEING PRESENT IN THE FORM OF A COMPOUND,AT LEAST ABOUT 0.07 OUNCE OF AT LEAST ONE ANION OF AN OXIDIZINGCOMPOUND, PHOSPHORIC ACID IN AN AMOUNT AT LEAST 15% IN EXCESS OF THEAMOUNT NECESSARY TO REACT WITH SUCH METAL, AND AT LEAST 0.0009 OUNCE OFCERIUM IN THE FORM OF A COMPOUND.